People seeking to lose weight or pack their daily diet with extra fruits and vegetables use smoothies routinely. Now, a new study suggests how thick you make your smoothie might impact how successful your weight-loss goals are.

The study, titled "Empty Calories and Phantom Fullness," was conducted by researchers at Wageningen University in the Netherlands. The participants, 15 men, were given a series of four different milkshakes to drink. The differences between each were calories (ranging from 100 to 500) and their viscosity (thick or thin). The men got an MRI after each milkshake, followed by questions every 10 minutes about their fullness.

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They found, unsurprisingly, that the lower-calorie shakes, even with the addition of fiber, left the stomach the fastest. The aspect that seemed to really change how the men reported their fullness was the thickness of the shakes. Even participants who drank the lowest-calorie thick drink reported feeling fuller than those who drank the high-calorie thin drink.

The term was coined "phantom fullness" by the study's author, and it's used to describe when one is satiated by a food's thickness instead of the energy density (calories).

As with any new area of study, more research is needed is find out which thickeners or types of fibers contribute best to feeling satiated. But this study demonstrates that people who feel fuller are less likely to load up on extra calories throughout the day. Now might be a good time to reduce the amount of milk you add to your smoothies to see if you can reap the reward of "phantom fullness."